Method of backing mill liners

ABSTRACT

A METHOD AND APPARATUS FOR BACKING MILL LINERS OF BALL MILLS AND THE LIKE WHICH INVOLVES THE APPLICATION OF A PLASTIC BACKING BETWEEN ABUTTING SURFACES OF MILL LINER AND MILL SHELL AND BETWEEN ADJACENT MILL LINERS, INCLUDING MECHANISMS FOR APPLYING A MIXTURE OF RESIN PASTE AND HARDENER PASTE FOR PROMPT BACKING APPLICATION.

23,1971 R. M. GREENBERG METHOD OF BACKING MILL LINERS Filed Sept. 16, 1968 f// i WZ a /W/ WM 14 nw 5 United States Patent Office Patented Feb. 23, 1971 3,565,715 METHOD OF BACKING MILL LINERS Robert M. Greenberg, Bayside, Wis., assiguor to Nordberg Manufacturing Company, Milwaukee, Wis., a corporation of Wisconsin Filed Sept. 16, 1968, Ser. No. 759,879 Int. Cl. B3211 35/00 U.S. Cl. 156-98 8 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for backing mill liners of ball mills and the like which involves the application of a plastic backing between abutting surfaces of mill liner and mill shell and between adjacent mill liners, including mechanisms for applying a mixture of resin paste and hardener paste for prompt backing application.

SUMMARY OF THE INVENTION This invention is in the field of mounting and backing the wearing parts of mills and the like, and is applicable to ball, rod and tube mills, and, in general, to mill or grinding structures in which replaceable wearing parts are applied within a rotating or moving mill shell or body.

A primary object is to provide a method of applying to mill liners a plastic backing which will harden after application and after the liner has been put in final position within the mill.

Another purpose is to provide a method of handling such liners before and during the application of the backing.

Another purpose is to provide a method of applying the backing to and about the securing means for the mill liners.

Another purpose is to provide an improved method of assembly of the liners and of the application of the backing to the liners, without the necessity of dismantling the mill, or removing the grinding charge.

Other purposes will appear from time to time in the course of the specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-section of a representative mill, indicating one step in the application of a new liner;

FIG. 2 illustrates a later step in the application of mixed resin and hardener paste to the appropriate surfaces of the liner;

FIG. 3 is a similar section illustrating a variant method of applying the mixed resin paste and hardener paste to the liner; and

FIG. 4 is a similar section illustrating the assembly of adjacent liner elements.

Like parts are indicated by like symbols throughout the specification and drawings.

DESCRIPTION OF THE MILL AND OF THE METH- OD OF APPLICATION OF THE RESIN PASTE AND HARDENER PASTE TO THE MILL Referring to FIGS. 1 to 4, inclusive, 1 generally in-- dicates a mill shell of a conventional type. It will be understood that in the use of the mill it is rotated about its longitudinal axis X by any suitable means, not herein shown. It will be understood that the interior of the mill is lined by a plurality of liners of a suitable metal, steel, manganese, or the like. Worn liners are indicated at 2, and new liners about to be applied, or in the course of application, are indicated at 3. The grinding media are indicated at 4. It will be understood that the media may be balls, tubes, rods, pebbles, or the like. It will be understood that the shell 1 is provided with a plurality of bolt apertures, such as the aperture 10 indicated in FIG. 1. These apertures are aligned with appropriate bolt apertures in the liners 3. Such an aperture 3a is indicated in FIGS. 1 to 4, it being understood that it may be enlarged, as at 3b, to receive the head of the securing bolt 11, shown as headed, at 11a, and as having an exterior securing nut 11b. It will be understood that in the course of the use of the mill the media, and the material undergoing grinding, which is fed in at the end or ends of the mill shell 1, effect a substantial wear on the liners used. The worn liners, indicated at 2, represent a terminal stage of the wear involved. These liners are, of course, held in position in relation to the mill by the securing bolts 11 and nuts 11b, but the inner surface is gradually worn down until liner replacement becomes necessary. It is important that this replacement be made as easy as possible, and with a minimum of down time.

An advantage of the present invention is that the used liners can readily be withdrawn, and replaced by new liners, without in any way dismantling or taking down the mill itself, or removing the grinding charge. The mill may be positioned with the charge gravitally supported on used liners, as is shown in FIGS. 1 to 4. Then, at, let us say, the upper right of these figures, some of the worn liners are removed by releasing the bolts 11 by loosening of the nuts 1112. An operator may conveniently enter the mill and remove the used liners, and pass them out through the mill end, or any appropriate hatch, or the like. As shown in FIG. 1, a new liner 3 may be positioned at an appropriate place, for example, by inserting through its apertures 3a the positioning and handling rod 12, the end of which may extend outwardly through the appropriate aperture 10 in the mill shell wall. An operator thus can readily position the new liner where it is to be secured, and, for example, by the use of the positioning and manipulating rod 12, may adjust temporarily the position of the new liner 3 to make its outer face accessible, if desired.

If the operator wishes to trowel the mixed resin and hardener paste he can then do so. A trowel 14 is diagrammatically illustrated in FIG. 2. the new liner 3 having been positioned to make its outer surface accessible to the operator, for the trowelling.

A suitable mix of resin paste and hardener paste may be supplied in any suitable manner to the operator, who then may trowel the rear surface of the member 3 and may then use the rod 12 to position it, to the final position in which it is shown, for example, in FIG. 1, there being a trowelled layer of the paste between the inner surface of the shell 1 and the abutting outer surface of the liner 3. Similarly, the edge surfaces of the member 3 may be trowelled and, if desired, the surfaces of adjacent new liners 3 may be separated by any suitable separators 15, of metal or the like. To avoid undesired adhesion, the

appropriate surfaces of the shell may be oiled. Similarly, the paste may be inserted in the securing aperture 3a byany suitable means, and the permanent securing member, the bolt 11, preferably oiled, may be inserted through the paste and secured by the exterior nut 11b. Thus each individual new liner 3 may be coated with the desired resin backing layer before it is permanently secured in place in the positions shown, for example, in FIGS. 3 and 4.

It will be understood that any suitable means for supplying the paste to the bolt holes may be employed. For example, I illustrate, in FIG. 3, a spouting element 01 gun .16 through which the mixture of resin paste and hardener paste may be applied, under fluid pressure, if desired, to the securing aperture of the line 3. Such a gun may also be used, if desired, to inject the hacking into the space between liner and shell.

The method is not limited to any specific formulae, but involves applying a plastic backing which may include a resin paste and a hardener, preferably to be mixed and applied on the job. I may, for example, employ a resin having a substantial proportion of an epoxy, with a suitable filler. I have found a mixing ratio of five parts resin to one part hardener, by weight or volume, to be convenient and practical, and to produce a cured product with satisfactory physical properties. Before mixing, the two elements are in a paste-like state, and may readily be mixed together by troweling, or otherwise. However, it will be understood that a wide variety of mixes may be employed, and a wide variety of mixing and application methods. The mixture provides a backing which can easily be applied, in paste form, between individual mill liners and the mill shell within which they are to be secured, but is amply hard when set. The mixed paste can also easily be applied between adjacent liners, or can be inserted Within or through the liner bolt holes. It should be kept in mind that the past practice was to use molten metals, most commonly zinc. The difficulty of handling molten zinc in a closed place, and the danger of fumes, make the task of application lengthy and dangerous. These difficulties are, of course, entirely obviated by my method.

Consider, first, the application by manual trowelling, as indicated in FIG. 2 After the pastes are mixed, the liner, which is being held in place against the side of the mill, for example, by the bar 12, may be swung forward into the position of FIG. 2. The paste is then trowelled onto the back, around the edges, and inwardly toward the center of the liner. When the liner is then tightened against the shell the backing is distributed properly. Backing is also forced into the open bolt holes, as shown in FIG. 3. The appropriate bolts 11, having been oiled, are placed in the epoxy-filled holes, holding the liner and freeing the bar. The bolts may then be exteriorly secured as by the nuts 11b. The paste can be placed on the top edge of the liner. Being thinner in section, its gel time on a cold metal surface will be extended to about forty minutes from the fifteen to twenty-minute characteristic of the material when applied in a thicker mass The mill may be slightly rotated, and the next higher liner may then be put in place, and the metal flat or strip 15, shown in FIG. 4, may be inserted between the adjacent liners. This procedure is repeated for the liners abutting the sides of the first liner, and, in each case, an appropriate volume is trowelled in position and inserted in the bolt hole. This method is satisfactory if the liners can be placed quickly. The material used must have a fast pot life and gel time, since it must cure quickly enough to be unaffected by the Water that is usually used to wash down the interior of the mill after the old liners are removed. The mills may be rotated step by step, and the application shown in FIGS. 1 to 3 may be conveniently maintained for the incremental addition of the new mill liners. It is not even necessary to remove the media, as they will simply ride on the newly inserted liners.

Under some circumstances, I find it advantageous to use a suitable gun-type device for applying the plastic backing. In this event the pressure applicator or gun shown at 16 in FIG 3 may be employed to deliver the entire charge. The paste can be filled into the gun 16 by a trowel or by pushing the material from a mixing table 30. Paste delivered by the gun can then be spread between the back of the liner and the abutting surface of the mill shell, by releasing the liner 3 to the trowelling position of FIG. 2. Assuming that a series of liners is in position, and have been gun-filled, it may or may not be necessary to place the paste initially on the sides of the liners. The bolt holes are filled as before, and the oiled bolts applied as above suggested. After a series of these gun-treated liners is in place the spaces btween them can easily be filled by the use of the gun. This provides a somewhat more flexible method than hand trowelling, since the gel time of the mix does not determine how quickly the next liner must be put in position. This also eliminates wasting material which cannot be used in time.

I will not go into detail on the gun, it being understood that its details may be widely varied. What is important is that a member 16, with a delivery aperture, should be provided, whereby the mix may, if desired, be shot in through the bolt hole, for distribution throughout the opposed surfaces of liner and mill.

To summarize the operation, during a step-by-step slow rotation of the mill steel liners positioned above the level of the media are removed and are replaced by new liners, the backing mix being plastically applied and the new liners being thereupon secured in permanent position. The plastic backing hardens to provide a firm support for the liners. A variety of mechanisms may be employed for mixing the plastic backing and for applying it, as above described and shown.

I claim:

1. The method of replacing worn backing liners for grinding mills and the like which includes rotating the mill to a position in which the charge rests gravitally on used liners, removing, at a level above the position of the charge, worn liners for replacement, loosely positioning a fresh liner in the place thus provided, applying a plastic backing material in paste form between the rear surface of the liner and the inner surface of the mill, distributing the backing material substantially uniformly throughout the opposed surfaces of the liner and mill, thereafter securing the liner in its final position, and indexing the mill from time to time and repeating the above steps until substantially the entire inner surface of the mill has new liners.

2. The method of claim 1 characterized by the step of employing a manipulating rod, passing through bolt holes of liners and mill, in order temporarily to position the new liner opposite its final location' but with its outer face accessible to the operator for the application of the layer of plastic backing material.

3. The method of claim 1 characterized by the step of initially spacing a new liner opposite its final position but with its outer surface exposed, applying a layer of plastic backing material to its initially accessible outer surface, and thereafter securing the liner in its final position with a substantially uniform layer of backing material throughout the closely opposed surfaces of the liner and mill.

4. The method of claim 1 characterized by the step of forcing the backing material through a bolt hole of the liner into the space between the outer surface of the liner and the opposite surface of the mill.

5. The method of claim 1 characterized by the step of forcing the backing material into the open bolt holes of the liner and thereafter inserting bolts through the backing filled bolt holes, and thereby securing the liner in its final position.

6. The method of claim 5 characterized by the step of oiling the bolts prior to their insertion through the plastic backing filled holes.

6 7. The method of claim 1 characterized by the steps Referen e Cit d of spacing the liner somewhat outwardly away from the UNITED STATES PATENTS opposite surface of the mill, trowelling a plastic backing on the outer surface of the liner sheet, and thereafter 3,325,045 6/1967 'f Q et securing the liner in permanent position in relation to the F 3,419,448 12/1968 Dlckmsm} milL 0 3,424,203 1/1969 Rubensteln l5694 8. The method of claim 1 characterized by the step of oiling surfaces of the mill to prevent undesired adhesion BENJAMIN BORCHELT Pnmary Exammer of the backing. S. C. BENTLEY, Assistant Examiner 

